 /*******************************************************************************
  * Copyright (c) 2003, 2005 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.ui.help;

 import java.net.URL ;

 import org.eclipse.help.IContext;

 /**
  * Abstract base class for the help system UI.
  * <p>
  * The Eclipse platform provides an extension point (<code>"org.eclipse.ui.helpSupport"</code>)
  * for plugging in a help system UI. The help system UI is an optional
  * component; applications may provide a UI for presenting help to the user by
  * implementing a subclass and including the name of their class in the
  * <code>&lt;config&gt;</code> element in an extension to the
  * <code>"org.eclipse.ui.helpSupport"</code> extension point.
  * </p>
  * <p>
  * Note that the standard implementation of the help system UI is provided by
  * the <code>"org.eclipse.help.ui"</code> plug-in. Since the platform can only
  * make use of a single help system UI implementation, make sure that the
  * platform is not configured with more than one plug-in trying to extend this
  * extension point.
  * </p>
  *
  * @since 3.0
  */
 public abstract class AbstractHelpUI {

     /**
      * Displays the entire help bookshelf.
      */
     public abstract void displayHelp();

     /**
      * Displays the help search facility. For backward compatibility, the
      * default implementation does nothing.
      *
      * @since 3.1
      */
     public void displaySearch() {
         // do nothing
 }

     /**
      * Displays the dynamic help for the active context. For backward
      * compatibility, the default implementation does nothing.
      *
      * @since 3.1
      */
     public void displayDynamicHelp() {
         // do nothing
 }

     /**
      * Starts the help search using the help search facility. For backward
      * compatibility, the default implementation does nothing.
      *
      * @param expression
      * the search expression
      * @since 3.1
      */
     public void search(String expression) {
         // do nothing
 }

     /**
      * Resolves the help resource href according to the help system
      * implementation.
      *
      * @param href
      * the help resource
      * @param documentOnly
      * if <code>true</code>, the resulting URL must point at the
      * document referenced by href. Otherwise, it can be a URL that
      * contains additional elements like navigation that the help
      * system adds to the document.
      * @return the fully resolved URL of the help resource or <code>null</code>
      * if not supported. Help systems that use application servers
      * typically return URLs with http: protocol. Simple help system
      * implementations can return URLs with file: protocol.
      *
      * @since 3.1
      */
     public URL resolve(String href, boolean documentOnly) {
         return null;
     }

     /**
      * Displays context-sensitive help for the given context.
      * <p>
      * (x,y) coordinates specify the location where the context sensitive help
      * UI will be presented. These coordinates are screen-relative (ie: (0,0) is
      * the top left-most screen corner). The platform is responsible for calling
      * this method and supplying the appropriate location.
      * </p>
      *
      * @param context
      * the context to display
      * @param x
      * horizontal position
      * @param y
      * verifical position
      */
     public abstract void displayContext(IContext context, int x, int y);

     /**
      * Displays help content for the help resource with the given URL.
      * <p>
      * This method is called by the platform to launch the help system UI,
      * displaying the documentation identified by the <code>href</code>
      * parameter.
      * </p>
      * <p>
      * The help system makes no guarantee that all the help resources can be
      * displayed or how they are displayed.
      * </p>
      *
      * @param href
      * the URL of the help resource.
      * <p>
      * Valid href are as described in
      * {@link org.eclipse.help.IHelpResource#getHref() IHelpResource.getHref()}
      * </p>
      */
     public abstract void displayHelpResource(String href);

     /**
      * Returns whether the context-sensitive help window is currently being
      * displayed.
      *
      * @return <code>true</code> if the context-sensitive help window is
      * currently being displayed, <code>false</code> if not
      */
     public abstract boolean isContextHelpDisplayed();
 }

